Narrative:

We were cleared by tower to fly heading 015 degrees after takeoff. Upon being cleared for takeoff; I ran up the throttles and hit toga for takeoff. The command bars came down and went back out of view. I hit the button 2 more times with similar results. I thought I had disengaged the toga by hitting it twice like I had. I finally just ignored the distraction and continued with the takeoff without the toga function. After taking off and passing 400 ft; I began a very shallow turn for the 15 degree assigned heading. We were coming up to the 1000 ft call to raise flaps to 1 degree when I noticed the heading flag on my HSI and the compass rose not moving. I xrefed with the pilot side and realized that I had overshot the heading assigned by about 15 degrees. I immediately turned to correct the heading and told the captain I had a problem with the display on my side. The captain started the APU in case there were electrical problems and we xferred aircraft control since his side seemed to be working correctly. We were given the departure control switch by tower and questioned why we had deviated on our heading assignment. We briefly told the tower that we had a display malfunction but didn't elaborate on the situation. After checking in with departure; we continued to troubleshoot the problem. Putting the APU generator on line didn't help; but using the compass/IRS xfer switch corrected the problem. We switched aircraft control again and were continuing the flight since things seemed to be operating normally on the assigned heading by departure control. We checked circuit breakers and got in the QRH for any further guidance. Upon further discussion; we decided that our next city would not have any maintenance and that we would ground the plane and make things worse down-line if we continued. We decided to return to ZZZ to repair the problem. When I tried to use the LNAV to go to the assigned points from ATC; I discovered that it was giving further erroneous information. I gave control of the aircraft to the captain and we continued with that for the rest of the flight. The rest of the flight was uneventful. Maintenance replaced the air data computer #2 and realigned the IRS to correct the problem after we taxied back to the gate. I believe that this would be very difficult to correct. Things happened so fast with so much going on in that critical phase of flight. The turn was so shallow that it was easy to overshoot; believing that I still had further turn to go. My concentration on the takeoff is on the ADI; not the HSI. By the time I noticed the warning flag for heading; we were already likely drifting through the assigned heading. I think the only thing that would have helped would be a quicker xchk by myself or the captain. I think the tower should have asked us to check our heading. He probably would have if there were any other aircraft being affected or if we hadn't corrected so quickly. I think this could easily happen again if the circumstances were repeated. I feel like this was a 'perfect storm' series of events leading up to the situation. Smarter people than me will have to come up with a better solution to prevent this from ever happening again.

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Original NASA ASRS Text

Title: B737 FO REPORTS HSI MALFUNCTION ON DEPARTURE CAUSING HEADING DEVIATION. OTHER RELATED PROBLEMS CAUSE FLT CREW TO ELECT TO RETURN FOR MAINTENANCE.

Narrative: WE WERE CLRED BY TWR TO FLY HDG 015 DEGS AFTER TKOF. UPON BEING CLRED FOR TKOF; I RAN UP THE THROTTLES AND HIT TOGA FOR TKOF. THE COMMAND BARS CAME DOWN AND WENT BACK OUT OF VIEW. I HIT THE BUTTON 2 MORE TIMES WITH SIMILAR RESULTS. I THOUGHT I HAD DISENGAGED THE TOGA BY HITTING IT TWICE LIKE I HAD. I FINALLY JUST IGNORED THE DISTR AND CONTINUED WITH THE TKOF WITHOUT THE TOGA FUNCTION. AFTER TAKING OFF AND PASSING 400 FT; I BEGAN A VERY SHALLOW TURN FOR THE 15 DEG ASSIGNED HDG. WE WERE COMING UP TO THE 1000 FT CALL TO RAISE FLAPS TO 1 DEG WHEN I NOTICED THE HDG FLAG ON MY HSI AND THE COMPASS ROSE NOT MOVING. I XREFED WITH THE PLT SIDE AND REALIZED THAT I HAD OVERSHOT THE HDG ASSIGNED BY ABOUT 15 DEGS. I IMMEDIATELY TURNED TO CORRECT THE HDG AND TOLD THE CAPT I HAD A PROB WITH THE DISPLAY ON MY SIDE. THE CAPT STARTED THE APU IN CASE THERE WERE ELECTRICAL PROBS AND WE XFERRED ACFT CTL SINCE HIS SIDE SEEMED TO BE WORKING CORRECTLY. WE WERE GIVEN THE DEP CTL SWITCH BY TWR AND QUESTIONED WHY WE HAD DEVIATED ON OUR HDG ASSIGNMENT. WE BRIEFLY TOLD THE TWR THAT WE HAD A DISPLAY MALFUNCTION BUT DIDN'T ELABORATE ON THE SITUATION. AFTER CHKING IN WITH DEP; WE CONTINUED TO TROUBLESHOOT THE PROB. PUTTING THE APU GENERATOR ON LINE DIDN'T HELP; BUT USING THE COMPASS/IRS XFER SWITCH CORRECTED THE PROB. WE SWITCHED ACFT CTL AGAIN AND WERE CONTINUING THE FLT SINCE THINGS SEEMED TO BE OPERATING NORMALLY ON THE ASSIGNED HDG BY DEP CTL. WE CHKED CIRCUIT BREAKERS AND GOT IN THE QRH FOR ANY FURTHER GUIDANCE. UPON FURTHER DISCUSSION; WE DECIDED THAT OUR NEXT CITY WOULD NOT HAVE ANY MAINT AND THAT WE WOULD GND THE PLANE AND MAKE THINGS WORSE DOWN-LINE IF WE CONTINUED. WE DECIDED TO RETURN TO ZZZ TO REPAIR THE PROB. WHEN I TRIED TO USE THE LNAV TO GO TO THE ASSIGNED POINTS FROM ATC; I DISCOVERED THAT IT WAS GIVING FURTHER ERRONEOUS INFO. I GAVE CTL OF THE ACFT TO THE CAPT AND WE CONTINUED WITH THAT FOR THE REST OF THE FLT. THE REST OF THE FLT WAS UNEVENTFUL. MAINT REPLACED THE ADC #2 AND REALIGNED THE IRS TO CORRECT THE PROB AFTER WE TAXIED BACK TO THE GATE. I BELIEVE THAT THIS WOULD BE VERY DIFFICULT TO CORRECT. THINGS HAPPENED SO FAST WITH SO MUCH GOING ON IN THAT CRITICAL PHASE OF FLT. THE TURN WAS SO SHALLOW THAT IT WAS EASY TO OVERSHOOT; BELIEVING THAT I STILL HAD FURTHER TURN TO GO. MY CONCENTRATION ON THE TKOF IS ON THE ADI; NOT THE HSI. BY THE TIME I NOTICED THE WARNING FLAG FOR HDG; WE WERE ALREADY LIKELY DRIFTING THROUGH THE ASSIGNED HDG. I THINK THE ONLY THING THAT WOULD HAVE HELPED WOULD BE A QUICKER XCHK BY MYSELF OR THE CAPT. I THINK THE TWR SHOULD HAVE ASKED US TO CHK OUR HDG. HE PROBABLY WOULD HAVE IF THERE WERE ANY OTHER ACFT BEING AFFECTED OR IF WE HADN'T CORRECTED SO QUICKLY. I THINK THIS COULD EASILY HAPPEN AGAIN IF THE CIRCUMSTANCES WERE REPEATED. I FEEL LIKE THIS WAS A 'PERFECT STORM' SERIES OF EVENTS LEADING UP TO THE SITUATION. SMARTER PEOPLE THAN ME WILL HAVE TO COME UP WITH A BETTER SOLUTION TO PREVENT THIS FROM EVER HAPPENING AGAIN.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.